This invention relates generally to the field of spraying devices, and more particularly to a sensing device for use with moving sprayers such as those used to apply liquid to powdered fertilizers, insecticides, herbicides, and the like. In this type of equipment, one or more spray nozzles is mounted on a truck or tractor, or a trailer pulled thereby, and the liquid or powder is applied over a relatively large area during each pass. It is important to know immediately if one or more of the nozzles has ceased operating. Otherwise, large areas will not be treated. It is often very difficult to determine whether a portion of a field has not been sprayed by visual observation after the task is completed. Therefore, it is very important that the operator of the vehicle know immediately when a nozzle ceases to spray.
In prior art systems, an operator continuously monitored the spray application by sight. This has several disadvantages. If the vehicle operator must continuously watch the sprayers, the safe operation of the vehicle is impeded. If a second person must be brought along for this task, the cost of the operation is increased. In some vehicles the sprayer nozzles are not easily seen from the driving position, and thus the operator cannot easily determine whether a spray nozzle has ceased to operate. Also, under many conditions, the movement of the vehicle causes considerable turbulance to be present in the vicinity of the spray nozzles, and it is difficult to determine which are spraying and which, if any, are not.
The prior art contains many systems for sensing the flow of a liquid. For some reason, these appear not to have been used in agricultural sprayers. The reasons for this probably include the expense of such an installation, and an inability to perform properly under the extremely rugged conditions of shock, vibration and contamination that are presented by agricultural apparatus. Furthermore, in this type of equipment, the sprayed material tends to become turbulent and coat the components of the device. An electrical sensing system operating in this environment must be able to withstand continuous abuse and must be designed to operate in a situation wherein the components are covered with the electrically conductive sprayed material, which can adversely affect the sensing system, causing it falsely to indicate always that spray is issuing from the nozzles. In any event, the many problems of this field have apparently not been overcome, for there appear to be no such sensing systems currently available.